Methods and systems for acoustically monitoring formations

Abstract

Methods and systems for acoustically determining reservoir parameters of subterranean formations. A tool comprising a plurality of acoustic sources and configured for acoustic measurements is deployed within a wellhole. Acquired acoustic data are processed and utilized for deriving key parameters for the formations. The plurality of acoustic sources include a plurality of hammer sources, where at least one of the hammer sources includes an actuator that is adapted to strike a surface to generate acoustic energy.

1. A system for taking acoustic measurements relating to subterranean formations, comprising:
 an acoustic tool comprising a plurality of acoustic sources mounted thereon, at least one of the acoustic sources comprising an actuator adapted to strike a surface to generate acoustic energy; 
 a conveyance configured for movement of the acoustic tool in a borehole traversing the subterranean formations; 
 at least one receiver configured to detect signals generated by the acoustic sources; 
 a computer in communication with the plurality of acoustic sources and the at least one receiver; and 
 a set of instructions executable by the computer that, when executed:
 process the acoustic measurements; and 
 derive parameters relating to the formation based on the acoustic measurements, 
 
 wherein the at least one acoustic source comprises a hammer source; 
 wherein the actuator comprises a solenoid and a solenoid plunger and the hammer source further comprises a sensor configured for sensing the position of the solenoid plunger; and 
 the system further comprising a processor configured for monitoring a current profile of the solenoid based on the position of the solenoid plunger. 
 
     
     
       2. The system of  claim 1 , wherein the at least one receiver is configured for detecting seismic signals. 
     
     
       3. The system of  claim 1 , further comprising:
 a controller section operably connected to the at least one receiver and configured to adjust data acquisition parameters; 
 a communications interface operably connected to the controller; 
 a processing unit, wherein the at least one receiver is configured to transmit electrical signals through the controller section and the communications interface to the processing unit, and 
 the processing unit is configured to perform signal processing using the electrical signals from the at least one receiver. 
 
     
     
       4. The system of  claim 1 , wherein the at least one receiver is located in a production well. 
     
     
       5. The system of  claim 1 , wherein the at least one receiver is located in an adjacent borehole traversing the subterranean formation; and
 the system is configured for crosswell data acquisition. 
 
     
     
       6. The system of  claim 1 , further comprising a coupling assembly configured for abutting the plurality of acoustic sources with the borehole wall. 
     
     
       7. The system of  claim 1 , further comprising a controller configured to synchronize firing of the plurality of acoustic sources and seismic signal detection of the at least one receiver. 
     
     
       8. The system of  claim 1 , further comprising a controller configured to control firing of the plurality of acoustic sources based on the location in the borehole of the acoustic tool. 
     
     
       9. The system of  claim 8 , wherein the controller is further configured to control the sources such that signals are generated at intervals of depth of the acoustic tool. 
     
     
       10. The system of  claim 1 , further comprising a plurality of shuttles wherein each shuttle includes a corresponding one of the plurality of acoustic sources. 
     
     
       11. The system of  claim 1 , wherein the actuator is adapted to strike a borehole wall to generate the acoustic energy. 
     
     
       12. A method for taking acoustic measurements relating to a subterranean formation, comprising:
 deploying a conveyance and an acoustic tool in a borehole traversing the subterranean formation, the acoustic tool comprising a plurality of acoustic sources, at least one of the acoustic sources comprising an actuator adapted to strike a surface to generate acoustic energy; 
 detecting seismic signals, generated by the plurality of acoustic sources, that are movable up and down in the borehole by the conveyance, at least one depth in the borehole; 
 processing the acoustic measurements; and 
 deriving parameters relating to the formation based on the acoustic measurements, 
 wherein the derived parameters relate to gas hydrates bearing formations and comprise dissociation front of the gas hydrates, 
 wherein the actuator comprises a position sensor to detect the position of the actuator. 
 
     
     
       13. The method of  claim 12 , further comprising determining a firing time of the plurality of acoustic sources by monitoring a current profile of a solenoid associated with each acoustic source. 
     
     
       14. The method of  claim 12 , wherein the acoustic tool further comprises a plurality of shuttles wherein each shuttle includes a corresponding one of the plurality of acoustic sources. 
     
     
       15. The method of  claim 12 , wherein the seismic signals are detected by deploying at least one receiver in a production well. 
     
     
       16. The method of  claim 12 , wherein the seismic signals are detected by deploying at least one receiver in an adjacent borehole traversing the subterranean formation; and
 the method further comprising configuring the acoustic tool and at least one receiver for crosswell data acquisition. 
 
     
     
       17. The method of  claim 12 , wherein the actuator is adapted to strike a borehole wall to generate the acoustic energy. 
     
     
       18. The method of  claim 12 , wherein the actuator comprises a solenoid with a plunger; and wherein the position sensor detects the position of the plunger.